1. Field of the Invention
The present invention relates to a radio system for allowing for exchanging messages between a set of relay stations and access stations for communications, the system using a least one common semaphore channel which is specifically provided to establish the connections between relay stations and access stations and through which the relay stations can transmit a first code signal at first predetermined instants, whereas the access stations comprise means for tapping the said channel at these predetermined instants.
2. Description of the Related Art
Such a system is known from the British Patent Specification 1 591 159. In this system the code signals are constituted by tones: a first tone for indicating that the relay station transmitting the tone wishes to send a message to the access stations which capture the tone and a second tone for indicating that the relay station transmitting the tone does not have a message to be broadcast. Thus, if one access station receives various tones of different relay stations, it will only be sensitive to the first tone if its level exceeds the tones received second.
This known system presents a first disadvantage due to the fact that it is ill-adapted to networks using a semaphore channel and transmitting messages of the digital type, as is the case with the RAMAGE network. This network is described in the article entitled: "RAMAGE - A Private Mobile Radio Telephone Network" by G. Banquet, J. P. Pittion, M. Coudreuse and published in "Commutation and Transmit No. 1,1986, pp. 19-30".